feat(third_party/cgit): Add derivation to build cgit

This is pretty much exactly the derivation from nixpkgs, with some
things removed to reduce the closure size (e.g. the various formatters
used in the default cgit version, which are replaced by cheddar in my
setup).

third_party/default.nix

@@ -24,6 +24,7 @@ let
       bashInteractive
       bat
       buildGoPackage
+      bzip2
       cacert
       cachix
       cargo
@@ -54,6 +55,7 @@ let
       lib
       lispPackages
       llvmPackages
+      luajit
       luatex
       makeFontsConf
       makeWrapper
@@ -91,6 +93,7 @@ let
       writeShellScriptBin
       writeText
       writeTextFile
+      xz
       zlib
       zstd;
   };